The traditional Fourdrinier papermaking process substantially includes three subsequent steps, carried out in corresponding sections of the papermaking machine: forming section, pressing section, drying section.
At the forming section, an aqueous pulp of cellulose fibers (and other possible components) is arranged on a so-called forming fabric or web shaped as a closed loop belt and supported by rollers. The water removal from the pulp through the forming fabric leads to the gradual formation of a wet paper material band with a still relatively high water content. A further water removal occurs at the pressing section, in which the paper material is pressed passing through one or more pairs of rollers. The paper material is then sent to the drying section for a last moisture removal. The so-formed paper is ready for the following steps of finishing and packaging.
Hereinafter, as customary in the field of papermaking and related fabric making, the terms “machine direction” (abbreviated “MD”) and “cross machine direction” (abbreviated “CMD”) are used to indicate a direction aligned with the feeding direction of the forming fabric in the papermaking machine and a direction parallel to the fabric surface and transversal (orthogonal) to the feeding direction, respectively. The direction or orientation of the warp and weft yarns of the forming fabric is also indicated with reference to machine direction and cross machine direction.
Furthermore, again as customary in the field, the surface of the forming fabric in contact with the cellulose pulp (i.e. with the paper material being formed) is meant to be the top surface of the fabric and the opposite surface facing the machine is the bottom surface. This reference will be also adopted to describe the vertical spatial arrangement of the yarns in the forming fabric.
Although various types of paper forming fabrics are known, in particular for use in the forming section, enhancement margins in this field still appear to exist, e.g. in terms of mechanical strength, stability, durability, draining capacity and quality of the formed paper.